This invention relates to a vacuum pickup device which operates in a relatively simple manner and which has relatively few parts. This invention particularly relates to a vacuum device which becomes operable, only upon its contacting an object that is to be picked up. This invention quite particularly relates to a vacuum device for picking up a sheet of material, especially a thin sheet of material, from a stack.
Heretofore, there have been many designs for a device to pick up an object, such as a sheet of material, by suction. In general, such a vacuum pickup device has been designed with an open end which does the actual picking up of the object. The open end of the vacuum pickup device typically has been connected to a source of vacuum, to make the device operable, just after the object, being picked up, covers the open end of the device. As a result, a vacuum pickup device generally has had to be provided with rather sophisticated controls for timing the connection of the source of vacuum to the open end of the device.
Frequently, materials handling equipment, provided with a plurality of such vacuum devices, has been used for picking up objects of varying sizes. However, a significant problem has arisen in the use of such equipment for picking up a relatively small object, which does not cover the open ends of all of the vacuum pickup devices of the equipment. In particular, the open ends of vacuum devices, which have not been covered by a relatively small object, being picked up, have drawn in air and thereby rendered the equipment inoperable for picking up the object. As a result, the uncovered open ends of vacuum devices in such equipment have had to be manually sealed before picking up a relatively small object.
In order to avoid the need for manually sealing the open ends of vacuum pickup devices, a design for a vacuum pickup device has been sought, in which a source of vacuum, connected to the device to make it operable, is not in communication with the open end of the device, unless the open end of the device is covered by the object to be picked up.